Unit 1 Flashcards
Define activation energy ?
The amount of energy required to start the reaction
What happens when temperature is increased.
At higher temperatures more particles have energy equal to or above the activation energy and so therefore there is more successful collisions
Enthalpy means
Enthalpy change means
Energy
Energy change
Symbol is (H)
What can catalysts be used for
They can lower the activation energy
Make the process more economical
The enthalpy change is ?
The enthalpy change is the start to end value difference
Define activated complex
The maximum energy point along the reaction path
On the graphs the shaded area represents all the molecules with energy greater than the activation energy. An increase in activation energy would cause a decrease in the shaded area
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How can covalent bond length be measured?
Covalent radius is ?
X-ray diffraction
The centre to the edge of the molecule. Not the bond length
Atomic size . Explain
Decreases across the periodic table - protons added moving across so there is a greater nuclear charge, with the same amount of shielding.
Increases down. - new electron shell added each time moves down
- greater shielding from the extra layer of electrons
What is an ion?
An ion is an atom which has lost or gained an electron
Define ionisation energy ?
Ionisation energy is the energy required to completely remove 1 mole of electrons from one mole of atoms in the gaseous state
When subbing in from data booklet make sure use state symbols
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Ionisation energy . Explain periodic table of This!
Decreases down:
- more electron shells and more shielding
- decreased attraction between outer electrons and nucleus, less energy required to move electron
Increases along:
- more protons added going across, so greater nuclear charge
- greater attraction between nucleus and outer electron being removed, so more energy required
Define electro negativity !
A measure of the attraction an atom ya for its bonding electrons
High electronnegativity :
Low electro negativity :
High - attracts electrons strongly
Low - attracts electrons weakly
Electro negativity on the periodic table. Explain.
Decreases down
- more electron shells being added and more shielding
- decreases attraction between outer electron and nucleus, so lower electro negativity
Increases
- more protons being added across so greater nuclear charge
- greater attraction between nucleus and outer electron being removed so more energy required
Group 0
Quick facts
- monatomic
- covalent bonds
- IMFs
Examples : helium and argon
Cov network
Carbon, silicon, boron
Fullerene is ?
A form of carbon which has a covalent molecular structure
Group 7
Quick facts
- bonding: covalent
- structure : molecular
- they are diatomic elements
Examples: fluorine, chlorine
Non polar covalent bonds are formed when?
Polar covalent bonds are formed when?
When the electronegativity values of each atom are the same (>0.4)
Formed when the electronegativity values of each atom are different
A difference in electronegativity causes a ?
Permanent dipole
And the more electronegative of the two molecules has the dots on the line nearest it and has a delta negative sign beside it
Polar shape is ?
Non polar shape is
Asymetrical
Symmetrical
More electrons means the higher the LDF is
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How are permanent dipoles formed?
Occur when electrons are unequally shared (electronegativity difference)
When does hydrogen bonding occur ?
When H is directly bonded to N, O, F
Must have line in between to be a hydrogen bond
Facts -
H2O, HF,NH3. All have higher boiling points due to the presence of hydrogen bonds between the molecules which means that more energy is required to overcome these intermolecular forces
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Why does ice float?
When water molecules form ice they create a large structure with large spaces between the molecules which results in it being less dense than water and so the ice floats
Reasons why an element has a higher boiling point than another ?
(Memorise word for word this)
The more electrons there are means the stronger the London dispersion force is. This makes it harder to break up the bonds, the further down the halogens, as the number of electrons increase.
Example :
Sulfur has a higher number of electrons than phosphorus meaning the London dispersion force is higher, making it harder to break intermolecular bonds. S8 has more electrons than P4, and so it has a higher London dispersion force
The more intermolecular forces, the more viscous a substance is (thicker)
Viscous means how thick it is
Example : syrup
Water is more viscous than ethanol because ?
Water CAN form hydrogen more hydrogens bonds
How to know what dissolves what ?
Polar dissolves polar
Non polar dissolves non polar
‘Like dissolves like’
Miscibility ?
Define miscible liquids
Define immiscible liquids
Miscible liquids is a liquid that can mix
Immiscible liquids can’t mix (I.e. oil and water)
The best group for being an oxidising agent is?
The best group for being a reducing agent is?
group 7 (halogens). Because they are very electronegative and also have a greater attraction for bonding electrons
Group 1 because they want to gain a full outer shell (metals)
Oxidising agents accept electrons
Reducing agents give electrons
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Balancing equations steps:?
- balance everything except oxygen and hydrogen
- balance Oxygen by adding H2O
- balance H by adding H+
- add electrons to same side as hydrogens to make charges equal on both sides
How are London dispersion forces formed/caused?
They are caused by the movement of electrons, as electrons move round the nucleus, one side of the atom becomes positive, and the other becomes negative for a fraction of a second. This causes a temporary dipole, this then causes a neighbouring atom to form an induced dipole for a fraction of a second
Are ionic lattices polar or non polar ?
Polar
